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GetDiagonal

This subroutine returns the diagonal entries of sparse matrix.

This Routine calls the Saad's sparse library.

  • offset: containing the offset of the wanted diagonal. The diagonal extracted is the one corresponding to the entries a(i,j) with j-i = offset. Therefore, offset = 0 means the main diagonal
  • diag : real array of length nrow containing the wanted diagonal. diag contains the diagonal (a(i,j),j-i = offset) as defined above.
  • idiag = integer array. It contains the poisitions of diagonal in the original arrays A. If idiag(i)=0 then it means that there was no diagonal found in row=i.
MODULE SUBROUTINE GetDiagonal( obj, A, diag, idiag, offset )
  TYPE( CSRSparsity_ ), INTENT( IN ) :: obj
  REAL( DFP ), INTENT( IN ) :: A( : )
  REAL( DFP ), ALLOCATABLE, INTENT( INOUT ) :: diag( : )
    !! Diagonal entries
  INTEGER( I4B ), ALLOCATABLE, INTENT( INOUT ) :: idiag( : )
    !! Position of diagonal entries in `A(:)`
  INTEGER( I4B ), OPTIONAL, INTENT( IN ) :: offset
    !! offset of the wanted diagonal
END SUBROUTINE GetDiagonal

The following routine is similar to the above routine, however, this routine does not return the position of diagonal in A.

MODULE SUBROUTINE GetDiagonal( obj, A, diag, offset )
  TYPE( CSRSparsity_ ), INTENT( INOUT ) :: obj
  REAL( DFP ), INTENT( IN ) :: A( : )
    !! Sparse matrix values
  REAL( DFP ), ALLOCATABLE, INTENT( INOUT ) :: diag( : )
    !! Diagonal entries
  INTEGER( I4B ), OPTIONAL, INTENT( IN ) :: offset
    !! offset of diagonal
END SUBROUTINE GetDiagonal